State-Interaction Pair-Density Functional Theory Can Accurately Describe a Spiro Mixed Valence Compound

Sijia S. Dong, Kevin Benchen Huang, Laura Gagliardi, Donald G. Truhlar

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Mixed-valence compounds with strong couplings between electronic states constitute one of the most challenging types of multireference systems for electronic structure theory. Previous work on a model mixed-valence compound, the 2,2′,6,6′-tetrahydro-4H,4′H-5,5′-spirobi[cyclopenta[c]pyrrole] cation, showed that multireference perturbation theory (MRPT) can give a physical energy surface for the mixed-valence compound only by going to the third order or by using a scheme involving averaging orbital energies in a way specific to mixed-valence systems. In this study, we show that second-order MRPT methods (CASPT2, MS-CASPT2, and XMS-CASPT2) can give good results by calculating the Fock operator for the zeroth-order Hamiltonian using the state-averaged density matrix. We also show that state-interaction pair-density functional theory (SI-PDFT) is free from the unphysical behavior of previously tested second-order MRPT methods for this prototype mixed-valence compound near the avoided crossing. This is very encouraging because of the much lower cost in applying SI-PDFT to large or complex systems.

Original languageEnglish (US)
Pages (from-to)2100-2106
Number of pages7
JournalJournal of Physical Chemistry A
Issue number10
StatePublished - Mar 14 2019

Bibliographical note

Funding Information:
K.B.H. is supported by College of Chemistry, Nankai University. The work of all authors is supported by the Air Force Office of Scientific Research grant no. FA9550-16-1-0134.

Publisher Copyright:
© 2019 American Chemical Society.


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